1. Field of the Invention
The present invention relates to a shaft accuracy measuring device for measuring accuracy of an output shaft of a motor.
2. Description of the Related Art
The output shaft of a motor is inserted through a front bearing and a rear bearing in a stator. There is a case in which the shaft accuracy of the output shaft is decreased depending on the assembly accuracy and the machining accuracy of the stator. More specifically, there is a case in which deflection (axial run-out), center deviation (center run-out), and inclination (face run-out) of the output shaft of the motor may occur. When the motor, whose shaft accuracy is thus decreased, is mounted onto a machine tool or the like, there is a tendency that vibration or abnormal noise is produced when the machine tool is driven, and the accuracy of machining by the machine tool is decreased as well.
As such, it is necessary to check the shaft accuracy of the motor after the motor has been assembled. More specifically, with a dial gauge attached to the motor or the motor shaft, the shaft accuracy is checked through the value of the dial gauge, while rotating the motor shaft.
However, when using a dial gauge, it is necessary for the operator to mount the dial gauge onto the motor or the like, adjust the gauge head of the dial gauge, and read and record the value of the dial gauge. Such an operation is cumbersome and time-consuming. As such, at a production site where many motors are manufactured, all of the many motors cannot be inspected, and thus sampling inspection is performed. Further, there is also a problem in which the measurement result differs depending on the operator's skill level.
Accordingly, Japanese Laid-open Patent Publication No. Hei 04-269601 and Japanese Laid-open Patent Publication No. Hei 05-227710 disclose a technique for measuring center run-out of the shaft of a motor in a non-contact manner using an electrostatic capacitance sensor. Further, Japanese Laid-open Patent Publication No. Hei 07-260425 discloses a technique for measuring run-out of a rotating body in a non-contact manner using a plurality of light projecting units and a plurality of light receiving units.